Klystron tuning means



Sept. 22, 1970 w. F. HUNTLEY \ET AL 3,530331 KLYSTRON TUN ING MEANS Filed April 14, 1969 INVENTORS WILLIAM-E HUNTLEY LEO J. POTTY xwwmm ATTORNEY United States Patent 3,530,331 KLYSTRON TUNING MEANS William F. Huntley, Waltham, and Leo J. Potty, Salem,

Mass., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Apr. 14, 1969, Ser. No. 815,729 Int. Cl. H01j /22 US. Cl. 3155.21 3 Claims ABSTRACT OF THE DISCLOSURE STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION Field of the invention This invention is directed to a tuning apparatus for a klystron tube. More particularly, it is directed to a tuniug apparatus which varies the resonant frequency of a klystron by varying the distance between the two grids which define the tubes interaction gap.

Description of the prior art In the prior art dual differential screw tuners were utilized to vary the distance between the grids defining the klystrons interaction gap. These tuners, however, did not take into account the mechanical backlash which results when the direction of tuner rotation is reversed.

When a tube utilizing the prior art tuner is tuned in one direction to a specific frequency and then the direction of tuning is reversed, there will be no repeatable frequency change for a certain amount of tuning motion in the new direction. This effect is known as backlash and results from the combined mechanical fits between all four active threaded members in the dual screw tuners. Even where accurately machined screws are utilized the backlash effect can vary considerably from tube to tube depending on the uniformity of individual parts.

Backlash is of particular concern when it is realized that tuning rate of the tubes involved is in excess of 100 mc. for a one-tenth of one percent change in the grid spacing. This spacing is of course a direct function of the spacing between the cathode and anode members of the tubes.

SUMMARY OF THE INVENTION The inventive tuner represents a significant advance over the prior art tuners. It utilizes a spring to overcome the backlash effect and requires only one differential device. The spring applies a constant torque in the same direction to the differential device. This eliminates mechanical play resulting from wear and manufacturer tolerances and requires no specially machined and fitted screws.

The inventive tuner utilizes only one differential device to move the cathode and anode blocks. Two resilient springs separated by 180 apply the torque to the block. The first spring is mounted at the differential device and 3,53%,331 Patented Sept. 22, 1970 p CC held in place thereby. The second spring is brazed to the two blocks.

In addition, the inventive tuner is more accurate and inexpensive than the prior art tuners. Since only one screw is used, only one adjustment is necessary. When two screws are used there is always the problem that one screw will be tightened more than the other. Furthermore, brazing the second spring to the anode and cathode blocks eliminates radial motion of the blocks and the resultant error therefrom. The savings cost is effected by the use of ordinary screws and the requirement of a single differential device in each tuner.

It is an object of the present invention to provide a new and improved tuner for klystrons.

It is a further object of the present invention to provide a highly accurate and relatively inexpensive klystron tuner.

It is a still further object of the present invention to eliminate backlash in differentially tuned klystrons.

Yet another object of the present invention is to provide a klystron tuner in which radial motion between the cathode and anode blocks is eliminated.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross-sectional view of a klystron utilizing the inventive tuner; and

FIG. 2 illustrates part of the components of the tuner.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, there is shown a reflex-klys tron tube 11. The tube has an anode block 12 and a cathode block 13.

An electron gun 14 is mounted in the cathode block. This gun has a cathode 1'5 and an accelerating :grid 16. The gun is powered through leads 17 and 18 from an external power source which is not shown.

The interaction gap of the klystron 20 is defined by two grids 19 and 21. Grid 19 is supported by the cathode block 13 while grid 21 is supported by anode block 12.

The repeller 22 is also mounted in anode block 12. It is powered through lead 23 by an external source.

The inventive tuning assembly is shown in FIGS. 1 and 2. As seen there, a bolt 24 is threaded into cathode block 12. The inside of this bolt is tapped to receive a second bolt 25 which is threaded into cathode block 13. A resilient spring 26 is placed between the two blocks and is tapped to allow passage of bolt 25. Nut 27 is threaded on bolt 25 to hold spring 26 against the cathode block and lock bolt 25 in position.

On the left side of the klystron a resilient spring 28 is brazed to the cathode and anode blocks and cooperates with a stop 29 attached to the cathode block. Stop 29 fixes the distance between the two blocks. Spring 28 serves to supply a bias to the cathode and anode blocks. and at the same time prevents radial motion between them. The cathode and anode blocks are machined to obtain the closest possible fit at the interaction gap. This machining together with the brazing of spring 28 to blocks 13 and 12 facilitates the use of a single set of tuning screws.

The klystron is adjusted by movement of bolt 24. When bolt 24 is turned down by a screwdriver or similar tool, anode block 12 is drawn against cathode block 13. Similarly, when bolt 24 is backed off, the two blocks separate. The movement of the two blocks varies the interaction of gap 20 between grids 19 and 21 and thereby varies the operating frequency of the klystron.

The outside pitch of bolt 24 is 40 threads per inch while its inside pitch and the outside pitch of bolt 25 are 48 threads per inch. This difference in pitch is characteristic of a differential screw and produces the displacement between the blocks described above.

In tests involving Raytheons QKK-547 reflex klystron tube, a variation in frequency in excess of 100 me. was observed for a change of one-tenth A of one percent in the grid spacing.

The bolts utilized are made from 303 stainless steel. The springs are made from #25 .040 beryllium copper which is first annealed, quenched in water and then tempered.

Thus, it is seen that a new and improved tuner has been provided for klystrons. The tuner is accurate and inexpensive. It can be utilized with any klystron when it is desired to vary its resonant frequency.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings.

What is claimed is:

1. A tuning apparatus for a klystron tube having first and second members which define an interaction gap between first and second grid electrodes mounted in said first and second members respectively, said grids and said members being movable with respect to each other for variance of the resonant frequency of said klystron tube, said tuning apparatus comprising a first bolt threadably mounted in said first member;

said first bolt being characterized by an internal threaded passageway;

a second bolt threadably mounted in said second body member and engaged with said internal threaded passageway in said first bolt; and

a first resilient spring for eliminating backlash mounted between said first and second members and having passageways through which said second bolt passes.

2. A tuning apparatus as in claim 1 said tuning apparatus further comprising a second resilient spring attachably mounted between said first and second members and a stop mounted on one of said blocks adjacent to said second resilient spring.

3. A tuning apparatus as in claim 2 wherein said first and second resilient spring members are U-shaped.

References Cited UNITED STATES PATENTS 2,515,280 7/1950 Varian 3155.22 X 2,686,890 8/1954 Davis 3155.22 X 2,862,138 11/1958 Larkin 3155.21 3,351,805 11/1967 Hoxie 3155.22

HERMAN KARL SAALBACH, Primary Examiner S. CHATMON, JR., Assistant Examiner US. Cl. X.R. 3l55.46, 5.53 

